The present invention relates to a current-fed isolation converter. Specifically, the current-fed isolation converter has a snubber circuit that regenerates energy stored in a snubber capacitor to an input level.
Japanese Patent Publication No. S62-203559 discloses a current-fed isolation converter. In the disclosed current-fed isolation converter, an excess voltage is applied to a switching element when the switching element is turned off. A snubber circuit is generally used to prevent the excess voltage from being applied to the switching element. However, when a conventional RCD snubber circuit, which is configured with a resistor (R), a capacitor (C), and a diode (D), is used, the efficiency of the convertor decreases. Thus, heat generation increases. In order to solve the above problems, Japanese Patent Publication No. 2001-54279 discloses a different type of snubber circuit. This snubber circuit regenerates energy stored at a snubber capacitor to an input level.
The snubber circuit disclosed in JP2001-54279 regenerates electric charge, which is stored in the snubber capacitor when the switching element is turned off, to a power source. The regeneration is performed by resonance of the snubber capacitor and a reactor. Thus, it is hard to set constant values for the circuit elements (the snubber capacitor and the reactor). In consideration of variations of the characteristics of the circuit elements, it is also hard to design the snubber circuit to stably perform.
An object of the present invention is to provide a current-fed isolation converter including a regeneration-type snubber circuit that stably performs and that has a simple circuit configuration or is implemented in a variety of ways.